Reinforced sods have long been known in the art. Sod mats of groundcovers, flowers, and playing field grasses are among the examples.
Molnar (U.S. Pat. No. 5,224,290) discloses flower and groundcover sod mats reinforced with nylon sod reinforcements. Decker (U.S. Pat. No. 4,986,026) discloses tall fescue sod mats which are very large and employ planting mediums containing straw and sewage sludge. Molnar (Application #07/745224) discloses flower and groundcover sod mats reinforced with polypropylene sod reinforcements. Milstein (U.S. Pat. No. 4,941,282) discloses wildflower sod mats reinforced with polyester fabrics. McFarland (U.S. Pat. No. 4,786,550) discloses a lightweight seed mat formed with melt blown nonwovens. Walton (U.S. Pat. No. 4,934,094) discloses a grass sod reinforced with netting. Decker (U.S. Pat. No. 4,336,668) discloses a novel method of growing groundcover sods reinforced with synthetic netting. Muldner (U.S. Pat. No. 4,190,981) discloses a complex lightweight seed mat using complex expensive equipment. Airhart in HortScience 18(1), 89-91, 1983 discloses groundcover and flower sods reinforced with synthetic netting.
In general, sod mats reinforced with synthetic spunbond fabrics are excellent all purpose sod mats. They have very good sod mat production characteristics, good strength and are easy to handle. The current synthetic spunbond reinforced sod mats use the inherent strength of the synthetic fabric to reinforce them. This often results in higher synthetic resin consumption and other limitations discussed herein.
Sod mats employing natural reinforcements such as straw, bark, or water sensitive glues can decompose prematurely if harvest time is delayed or if the planting medium is particularly biologically active. Furthermore, the time at which degradation begins is difficult to control.
Sod mats employing synthetic netting for reinforcement can produce good sod mats. They do however, suffer from some important drawbacks. If the netting openings are large, harvest is usually delayed while if the netting openings are small, the roots of the plants can be girdled, Neither leads to sod mats with both optimum sod mat production and growing characteristics.
In view of the above prior art, there still exists a need for specialty sod mats which combine the advantages of early harvest time, good "shelf life" stability, and which are easy to handle and propagate. Improved control of degradation timing for at least some of the reinforcement is desired to improve "shelf life" stability of sod mats wherein a portion of the reinforcement is degradable. Furthermore, sod mats which place reduced demands on the strength of the synthetic reinforcement are needed to reduce synthetic resin consumption and in general, to reduce costs. Objects of the current invention are then to develop a select group of preferred specialty sod mats along with their method of manufacture which are easy to handle, have good "shelf life" stability, and place reduced demands on the strength of the synthetic reinforcement. Another object of the invention is to develop sod mats with improved control of degradation timing for a portion of the reinforcement to improve "shelf life" stability. It is also an object of this invention to develop a manufacturing process for these specialty sod mats with good production characteristics.
Other objects and advantages of the current invention will become more apparent to those skilled in the art in view of the following description and examples.